1. Field of the Invention
The present invention relates to a three-dimensional display device, and more particularly, relates to a volumetric type three-dimensional display device.
2. Background of the Related Art
A three-dimensional display uses technology that allows an observer to perceive a three-dimensional effect from a two-dimensional image. This technology has been widely utilized in display-relevant technical fields as well as home appliances, communication, aerospace, art and automobiles. To achieve a three-dimensional effect, a parallax of both eyes, namely, a distance of 65 mm, acts as a primary factor, and mental state and memory act as other factors. Thus, according to three-dimensional information transferred to a user, a three-dimensional display technology may be divided into a volumetric type, a holographic type and a stereoscopic type. Of these types, the volumetric type is suitable for an I-MAX film and has the advantage of supplying large-sized display images.
FIG. 1 is a view schematically illustrating a volumetric type three-dimensional display device 10 according to the related art. As shown in FIG. 1, the volumetric type three-dimensional display device 10 includes first to fourth display portions 20, 30, 40 and 50. The first to fourth display portions 20, 30, 40 and 50 display first to fourth partial images I1, I2, I3 and I4, respectively. The first to fourth partial images I1 to I4 are produced by dividing one image according to depths of the one image. A user 60 synthesizes the first to fourth partial images I1 to I4 as a three-dimensional one image. Also, the user 60 adds positions of the first to fourth display portions 20 to 50, namely, distances from the user 60 to the first to fourth display portions 20 to 50, into image information of the first to fourth partial images I1 to I4, thereby perceiving the one image as a three-dimensional image.
However, the related art volumetric type three-dimensional display device 10 has the following limitations and disadvantages. Each display portion should display the display image produced by itself, and also should transmit the display images produced by the display portions behind it. Specifically, the second display portion 30 should transmit the first partial image I1 produced by the first display portion 20, the third display portion 40 should transmit the first and second partial images I1 and I2 produced by the first and second display portions 20 and 30, and the fourth display portion 40 should transmit the first to third partial images I1 to I3 produced by the first to third display portions 20 to 30. Accordingly, qualification of the display portion is limited. For this reason, emissive type display devices, such as organic electroluminescent display devices, field emission display devices, plasma display devices and the like, can not be used as the display portion of the volumetric type three-dimensional display device.
While a non-emissive type display device, such as a liquid crystal display device, can be used for the display portion, it is difficult to set up a light source such as a backlight unit. When the non-emissive type display device has a low transmissivity, the partial images should pass through a plurality of non-emissive type display devices, thereby decreasing the brightness. Accordingly, a projection type display device is used as the display portion. The projection type display device generally needs a large complicated optical portion and a screen where an image is projected. When the projection type display device is adopted for the volumetric type three-dimensional display device, a distance between the screens should be long enough to set up the optical portion. However, due to the long distance, the user may not normally perceive the three-dimensional one image synthesized from the partial images.